Glucagon carbohydrate metabolism

Storage and utilization of tissue glycogen, maintenance of blood glucose concentration, and other aspects of carbohydrate metabolism are meticulously regulated by hormones, including insulin, glucagon, epinephrine, and the glucocorticoids. 

Glucagon is a second pancreatic hormone that, like insulin, influences carbohydrate metabolism. However, most of its actions oppose those of insulin. The enkephalins and endorphins are the body s natural painkillers they are thought to be responsible for runner s high. These, among many others, are proteins or are closely related to them. 

The signal is often modulated by integration with input from other signaling pathways (eg, the insulin/glucagon ratio is important for balancing carbohydrate metabolism in the liver). 

Effects on carbohydrate metabolism The intravenous administration of glucagon leads to an immediate rise in blood glucose. This results... 

Glucocorticoids probably have more than one effect on carbohydrate metabolism. An increase in fasting glucagon... 

Somatostatin. Somatostatin, also called growth hormone-inhibiting hormone, is a 14-amino-acid peptide found in the gastrointestinal tract, the hypothalamus, and the 6-cells of the pancreatic islets. Although somatostatin does not appear to have a direct effect on carbohydrate metabolism, it inhibits the release of growth hormone from the pituitary. In addition, somatostatin inhibits secretion of glucagon and insulin by the pancreas, thus modulating the reciprocal relationship between these two hormones. 

A number of mechanisms have been proposed for the action of insulin in reversing glucagon-stimulated phosphorylation of the enzymes of carbohydrate metabolism. From the student s point of view, the ability of insulin to reverse glucagon-stimulated phosphorylation occurs as if it were lowering cAMP and stimulating phosphatases that could remove those phosphates added by protein kinase A. In reality, the mechanism is more complex and still not fully understood. 

Three hormones play a part in the regulation of carbohydrate metabolism epinephrine, glucagon, and insulin. Epinephrine acts on muscle tissue to raise levels of glucose on demand, while glucagon acts on the liver, also to increase the availability of glucose. Feedback control plays a role in the process and ensures that the amount of glucose made available does not reach an excessive level (Section 24.3). The role of insulin is to trigger the feedback response that achieves this further control. 

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